JPS59161157A - Digital processing type phase modulating circuit - Google Patents

Abstract

PURPOSE:To eliminate the analog element of a modulating circuit, and applying directly the phase of a modulated wave with a digital control in accordance with an input data sequence, and to generate easily a modulated wave whose phase is discontinuous, too, by changing a controlling method in a selecting circuit. CONSTITUTION:In according with an input an input data sequence from an input terminal 21 of a digital processing type phase modulating circuit; a phase variation is given to a desired modulated wave by a selecting circuit 22. Also, an output of a fixed oscillator 17 is frequency-divided into 2<n> by a frequency dividing circuit 18, and a carrier wave (frequency: f0/2<n> Hertz) whose phase is different by 2pi/2n radian is generated by 2<n> waves. Those carrier waves of 2<n> waves are provided to a switching circuit 20 to which a selecting signal from the selecting circuit 22 is inputted. Subsequently, a carrier wave having a desired phase is extracted from carrier waves 19 of 2<n> from the frequency dividing circuit 18, basing on a selecting signal from the selecting circuit by the switching circuit 20, outputted to a modulated wave output terminal 23, and modulated wave whose phase is discontinuous is also generated easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital processing type phase modulation circuit that obtains a modulated signal by smoothly changing the phase of a carrier wave according to an input data signal sequence.

Conventional circuits of this type generate a modulated wave with a constant envelope and continuous phase in order to obtain a narrow-band modulated wave with less deterioration due to nonlinearity in the transmission system. As shown, a circuit has been proposed in which an input data signal is waveform-shaped using an analog filter, thereby frequency-modulating a carrier wave. Here, 1 is a data input terminal, 2 is a baseband waveform shaping filter, 3 is a frequency modulator, and 4 is a modulated wave output terminal. This modulation circuit is configured so that the time change in the phase of the modulated wave has the characteristics shown in Figure 2 for a binary human input data series (-1, -1,...). ing.

However, since such a modulation circuit uses an analog-pig type baseband waveform shaping filter, it is difficult to adjust and suffers from deterioration due to aging.

Another conventionally used circuit of this type is the orthogonal modulation circuit shown in FIG. 3, which is an improved version of the circuit shown in FIG. Here, 5 is a data input terminal,
6 is a signal generation circuit, 7 and 8 are mutually orthogonal signal waves output from the signal generation circuit 6, 9 and 10 are mixers, and 11
is a carrier wave input terminal, 12 is a 90° phase shifter, 13, 14
are mutually orthogonal carrier waves, 15 is a power coupler, and 16 is a modulated wave output terminal.

Depending on the data series input from the data input terminal 5,
The phase change of the modulated wave is a phase change φft as shown in Figure 2.
The signal generation circuit 6 generates and outputs a signal wave shown in the following equation so that the signal waveform is 1.

Signal wave 7... section [φ(tl) Signal wave 8...
...sIn [φ(t)] where φftl is the phase change of the modulated wave.

These signal waves generate a carrier wave 11 expressed by the following formula:
, 12 are orthogonally modulated.

The signal wave output from the power coupler 15 is given by the following equation.

sin (ω.t+φ(t)) Therefore, the phase of the modulated wave can be changed as shown in FIG. 2 according to the input data sequence.

However, in this circuit, analog mixers must be used in the mixers 9 and 10, which causes deterioration due to nonlinearity of the mixers, offset drift, and aging. Furthermore, if the orthogonal relationship between the carrier waves 13 and 14 is no longer satisfied, there is a drawback that the output waveform similarly deteriorates.

In order to solve these drawbacks, the present invention provides a digital processing type phase modulation circuit that eliminates the analog elements of the modulation circuit and directly digitally controls the phase of a modulated wave according to an input data series. It is something.

The present invention will be explained in detail below with reference to the drawings.

FIG. 4 shows an embodiment of the present invention, in which 17 is a fixed oscillator;
18 is a frequency dividing circuit, 19 is a carrier wave signal, 20 is a switching circuit,
21 is a data input terminal, 22 is a selection circuit, and 23 is a modulated wave output terminal.

A fixed oscillator (frequency f, hertz) 17 is frequency-divided by n (n is a positive integer) by a frequency dividing circuit 18 to generate 2n types of carrier waves 19 whose phases differ from each other by lc2π/2n radians. FIG. 5 represents the 19 generated carrier wave signals on a phase plane.

Next, in order to give a desired phase change to the modulated wave according to the data series inputted from the input terminal 21, the selection circuit 22 selects one specific wave among the 2n carrier waves generated by the frequency dividing circuit 8. and the selection signal (n bits) is sent to the switching circuit 2.
Output to 0. Based on the selection signal from the selection circuit 22, the switching circuit 20 extracts a carrier wave having a desired phase from the 2n carrier waves 19 and outputs it to the modulated wave output terminal 23.

Therefore, in this circuit, in order to obtain the desired phase change of the modulated wave as shown in FIG. 6 fal, the phase change shown in FIG. 6 fbl is output. Since this circuit has such a configuration, the input catheter signal is waveform-shaped as shown in Fig. 1, and the carrier wave is frequency-modulated to achieve the desired phase change of the modulated wave. Functions equivalent to the method obtained can be realized using an all-digital circuit.

As explained above, according to the present invention, it is possible to generate various modulated waves with approximately constant envelopes and continuous phases, and since it is an all-digital circuit, it can be easily implemented into a K LSI. This has the advantage that there is no need for circuit adjustment and there is no problem of deterioration due to aging.

Note that according to the present invention, modulated waves with discontinuous phases can be easily generated by changing the control method in the selection circuit.

Furthermore, in the present invention, a case has been described in which carrier waves whose phases differ from each other by 2π/2n (n is an integer) radians are generated by a frequency divider circuit, but in general, carrier waves whose phases differ from each other by 2π/M (M is an integer) radians are generated. It may also be generated by a frequency dividing circuit.

[Brief explanation of drawings]

Figure 1 shows a conventional baseband waveform shaping modulation circuit;
The figures explain the operation of the modulation circuit shown in Fig. 1. 6-No-time time chart; Fig. 3 is a block diagram showing a conventional quadrature modulation circuit; Fig. 4 is a pop-up diagram showing an embodiment of the present invention; FIG. 5 shows 2n (n=
Fig. 6 fat is a time chart showing the time change of the modulated wave phase required for the modulation circuit of the present invention, Fig. 6 (bl is the diagram representing the present circuit) It is a time chart showing the time change of the modulated wave phase generated by 1... Take input terminal, 2... Baseband waveform shaping filter, 3... Frequency modulator, 4...
Modulated wave output terminal, 5...Data input terminal, 6...
・Signal generation circuit, 7, 8... Output signal waveform, 9
, 10... mixer, 11... carrier wave input terminal,
12...90° phase shifter, 13, 14...mutual...
Carrier wave orthogonal to 15...Power coupler, 16...
・Modulated wave output terminal, 17...Fixed oscillator, 18...
Frequency dividing circuit, j9... divided carrier wave, 20...
・Switching circuit, 21... Take input terminal, 22...
・Selection circuit. Patent applicant Nippon Telegraph and Telephone Public Corporation agent Tsuneo Shiramizu and one other person 7- H42/G359- , A, -2

Claims (1)

[Claims] A modulation method that obtains a modulated signal by shaping the waveform of an input data signal and smoothly changing the carrier phase, which includes a fixed oscillator (frequency f.hertz) and the output of the fixed oscillator divided by 2n. carrier waves (where n is an integer) whose phases differ from each other by 2π/2n radians in the frequency-divided signal (where n is an integer).
Frequency f. /2n hertz), a switching circuit that extracts one specific wave from the 2n waves of the frequency dividing circuit, and a control that causes the switching circuit to sequentially select the specific one wave. What is claimed is: 1. A digital processing type phase modulation circuit comprising a selection circuit that performs the following based on a human data series. 1-